Water-bearing explosive containing nitrogen-base salt and method of preparing same



nited States Patent 3,431,155 WATER-BEARING EXPLOSIVE CONTAININGNITROGEN-BASE SALT AND METHOD OF PREPARING SAME Colin Dunglinson andWilliam M. Lyerly, Hagerstown,

Md., assignors to E. I. du Pont de Nemours and Company, Wilmington, DeL,a corporation of Delaware No Drawing. Filed June 2, 1967, Ser. No.643,064 US. Cl. 149-47 17 Claims Int. Cl. C061; ]/04, 21/00, 11/00ABSTRACT OF THE DISCLOSURE Water-bearing explosives comprising nitrogenbase salt sensitizer and a process for their manufacture employing thecrude aqueous reaction product of nitrogen base and oxidizing acid.

Background of invention Water-bearing explosives have found wideacceptance in recent years. These products typically comprise anoxidizing component, usually predominantely ammonium nitrate, and a fuelcomponent dispersed or dissolved in an aqueous medium which is normallythickened or gelled. The high strength, high velocity water-bearingexplosives used where premium performance is required additionallycontain a high explosive, e.g., TNT, or a metallic fuel, e.g., aluminum,as at least part of the fuel component. Not only do such materials actas fuels, but also they increase explosive strength and, particularly inthe case of high explosives and finely divided metals, also increasesensitivity.

Use of the aforementioned high explosives and metallic additivespresents some problems. First, such additives are expensive and, thus,use of such products is often restricted on a purely economic basis.However, without such additives, products of relatively low explosivesstrength result. Second, the aforementioned metallic and high explosiveadditives are usually solids which must be dispersed through theexplosive during manufacture and maintained dispersed throughout storageand use. Segregation of metallic and high explosive constituentsadversely affects explosive properties and, in the case of highexplosive sensitizers, may create a safety hazard. Finally,incorporation of insoluble solid high explosives and metallic fuels inwater-bearing explosives is more difficult and expensive than theincorporation of corresponding liquid or soluble components.

Summary of invention This invention provides improved high-performancewater-bearing explosive of low cost. For water-bearing explosives, theproducts of this invention has a surprisingly high detonation velocityand brisance end, thus, are particularly adapted for hard shootingconditions. These advantageous properties are obtained with the productsof this invention over a wide range of densities including those as highas 1.4 g./cc. or higher. Preferred products of this invention containsensitizers which are liquid or, if solid, soluble or readilydispersable in the aqueous phase of the explosives, and, hence, haveinherent advantages in manufacture and storage. More specifically, thisinvention provides an improvement in water-bearing explosives comprisingan inorganic oxidizing salt component, a fuel component and water, saidimprovement comprising incorporating in said explosives a sensitizercomponent comprising at least one salt of an inorganic oxidizing acid,preferably nitric acid, and a base selected from the group consisting of(a) acyclic nitrogen bases having no more than two hydrogen atoms bondedto the basic nitrogen and up to three carbons per basic nitrogen and (b)phenyl amines, said salt having an oxygen balance more positive thanl50%, said sensitizer component comprising, other than said salt, lessthan about 50% by weight of high explosive sensitizer.

Oxidizing and fuel components are used herein in their conventionalsense to refer to materials in the explosives which have positive andnegative oxygen balances, respectively. Oxygen balance as used hereinrefers to the percent excess or deficiency of oxygen required forcomplete combustion and is calculated as the molecular weight of oxygenrequired or given off in complete combustion divided by the molecularweight of the material in question. Sensitizer as employed herein refersto a material which when removed from an explosive in small (e.g., a fewpercent), incremental amounts substantially reduces the sensitivity ofthe explosive at its critical diameter at a given temperature of test.

Description of preferred embodiments The nitrogen base salts employed inthis invention can be derived from inorganic bases such as hydrazine butpreferably are derived from aliphatic amines and phenyl amines. Phenylamines as used herein refers to compounds having one carbocyclicaromatic ring to which is bonded at least one, and preferably one ortwo, primary amino groups. Salts of primary, secondary and tertiaryamines meeting the aforementioned requirements can be used. Although thebase moiety can bear substituents other than carbon, hydrogen and thebase nitrogen inert with the system, those consisting of carbon,hydrogen and the aforementioned basic nitrogen are preferred. Because ofavailability, low cost, ease of handling and manufacture and excellentexplosive properties of the products of this invention made therefrom,salts of saturated aliphatic amines of up to three carbons arepreferred. The oxidizing acid moiety can be that of any of the stronginorganic oxidizing acids, preferably mineral acids, and such as, forexample, salts of nitric, nitrous, chloric, and perchloric acids. Thoseacids having an oxygen balance of at least about +10% are preferred.Nitrates are particularly preferred because of their ready availabilityand excellent sensitizing effect.

Examples of salts which can be used in the sensitizing component includeinorganic salts such as hydrazine nitrate, dinitrate, and perchlorate;salts of aliphatic amines such as monomethylamine nitrate, nitrite,chlorate, and perchlorate, ethylenediamine dinitrate and diperchlorate,dimethylamine nitrate, trimethylamine nitrate, ethylamine nitrate,propylamine nitrate, guanidine nitrate and urea nitrate and salts ofphenyl amines such as aniline nitrate, chlorate and perchlorate,p-chloroaniline nitrate and phenylenediamine dinitrate. Of theaforementioned salts monomethylamine nitrate, trimethylamine nitrate andethylenediamine dinitrate are particularly preferred because of the easeof formulation of explosives therewith and the outstanding explosiveproperties including velocity and strength of the resulting products.Mixtures of the aforementioned salts can be used as well as mixtures ofone or more of such salts with other similar salts having an oxygenbalance more negative than l50%, for example, cyclohexylamine nitrateand diethylamine dinitrate. Normally, in such salt mixtures, the overalloxygen balance of the salt should be more positive than -l50%.

The nitrogen-base salts can be incorporated in the explosives of thisinvention in substantially pure form; however, they can be, andpreferably are, provided as a crude reaction mixture of the basesubstantially neutralized with oxidizing acid, either formed separatelyin aqueous medium then blended with the remainder of the constituents ofthe explosive or formed in situ in the presence of one or more of suchconstituents. Thus, a preferred embodiment of this invention provides animprovement in the process for preparing water-bearing explosives whichcomprises blending oxidizing and fuel components with water, whichimprovement comprises blending with the ingredients of said explosivethe product obtained by neutralizing one or more of the aforementionednitrogen bases with one or more of the aforementioned oxidizing acids.

A characteristic feature of the explosives of this invention is thatthey require none of the conventional high explosive sensitizers ormetallic-fuels characteristically required for premium performance inhigh velocity, high strength water-bearing explosives. Thus, althoughmetals such as finely divided aluminum or high explosives such as TNT,PETN, RDX, HMX, or mixtures thereof such as pentolite (PETN/TNT) andComposition B (TNT/ RDX) can be used as a minor part of the sensitizercomponent, they are not required and, in the preferred case, areavoided. If such conventional high explosives are employed, theyconstitute less than about 50% of the total weight of sensitizer. Someof the amine salts used in the compositions of this invention are highexplosives, i.e., detonating explosives per se. However, both highexplosive salts as well as those that are not explosives per se, so longas they meet the aforementioned criteria, can be used alone or incombination in the sensitizer component of the subject products.

The total amount of nitrogen-base salt used varies with the particularcomposition and can range from 5 to 90% by weight of the totalcomposition. In general, the amount of salt decreases as the amount ofwater used is reduced and as the amount, if any, of auxiliary sensitizeris increased or as a lower strength product is desired. Preferably,about to 50% of the salt sensitizer is used. Depending on its oxygenbalance, the amine salts in addition to being the primary sensitizer,are a part of the oxidizing or fuel component, normally the latter.

In its broad aspects the improvement of this invention can be applied toany of the known general types of inorganic salt based water-bearingexplosives having a continuous phase comprising water, and theexplosives of this invention can contain the conventional ingredientsnormally employed in such water-bearing explosives in the amountsgenerally used therein. As the primary oxidizing ingredients, thecompositions of this invention usually contain at least about by weightof inorganic oxidizing salt. Examples of inorganic oxidizing saltsinclude ammonium, alkali metal and alkaline earth metal nitrates andperchlorates as Well as mixtures of two or more such salts. Examples ofsuch salts are ammonium nitrate, ammonium perchlorate, sodium nitrate,sodium perchlorate, potassium nitrate potassium perchlorate, magnesiumnitrate, magnesium perchlorate and calcium nitrate. Preferably, when aninorganic oxidizing salt is used as the oxidizing component, suchcomponent contains at least 45% of at least one salt which is highlysoluble in water at room temperature, that is, at least as soluble asammonium nitrate, and preferably, the aqueous phase in the compositionscontains a substantial portion of oxidizing salt, for example, 40 to 70%by weight thereof at room temperature. Inorganic oxidizing salt mixturescontaining at least about 50% by weight of ammonium nitrate and at least5% by weight of sodium nitrate are particularly preferred.

The nitrogen base salt sensitizer can provide substantially all of thefuel component. Often, however, it is desirable to include one or moreof the conventional fuels as auxiliary fuels. Auxiliary fuel or fuelsused in the compositions of this invention can be varied widely,provided that in the composition in which any particular fuel is used,the fuel is stable, that is, prior to detonation, during preparation andstorage, the fuel is chemically inert with the system. In addition tothe aforementioned highexplosive auxiliary sensitizers examples ofauxiliary fuels are sulfur and carbonaceous nonexplosive fuels such asfinely-divided coal and other forms of finely-divided carbon and solidcarbonaceous vegetable products such as cornstarch, wood-pulp, sugar,ivory nut meal and bagasse. Examples of auxiliary metallic fuels arealuminum and iron, and alloys of such metals such as aluminum-magnesiumalloys, ferrosilicon, ferrophosphorous, as well as mixtures of theaforementioned metals and alloys. Preferably, the total amount of fuelis adjusted so that the total composition has an oxygen balance of aboutfrom 25 to +10% and, except for those compositions containing theaforementioned heavier metallic fuels such as ferrophosphorus andferrosilicon, preferably the oxygen balance is between about l0 and+10%.

As is conventional in water-bearing explosives, the compositions of thisinvention contain at least about 5% by weight of water. Thewater-bearing compositions to which this invention is directed generallycontain less than about 50% by weight of water and, preferably, on theorder of about .10 to 30% by weight of water based on the totalcomposition.

Conventional materials also can be used to thicken or gel the aqueousphase. Of such materials, galactomannans, especially guar gum, areparticularly preferred. Usually about from 0.1 to 5% of suchgalactomannan based on the total weight of composition is employed.Galactomannans also preferably are crosslinked with an oxidizing agentsuch as an alkali metal dichromate either alone or in combination with asoluble antimony compound. Guar gum in combination with polyacrylamideis often preferred for pourable explosives.

As previously indicated, the compositions of this invention arepreferably prepared using the crude reaction product obtained byneutralizing nitrogen base with oxidizing acid in aqueous medium. Theproduct is conveniently blended with a concentrated substantiallysaturated solution of the oxidizing components optionally withthickeners incorporated therein, then optional additives such asauxiliary fuels and sensitizers blended therewith. Finally, crosslinkingagents are added just prior to packing, in the case of packagedproducts, and just prior to loading into the borehole in the case ofpump-truck products. Alternately, the nitrogen base salt can be formedin situ in the presence of other ingredients of the explosive,particularly the oxidizing component. With ammonium nitrate basedexplosives, preferably pH is adjusted to about from 4 to 7. Watercontent can conveniently be controlled by the concentration of theoxidizing acid added to neutralize the nitrogen base.

In the following examples which further illustrate this invention partsand percentages are by weight unless otherwise indicated.Monomethylamine nitrate is indicated by MMAN and ethylenediaminedinitrate by EDAN. PAT designates potassium antimony tartrate. AN isammonium nitrate.

EXAMPLES 13 Water-bearing explosives of the compositions shown in Table1, in parts, are prepared in a mixer from the ma terials listed by thefollowing sequence of steps:

(1) Ammonium nitrate liquor (about ammonium nitrate), solid ammoniumnitrate if required, and aqueous solution of amine nitrate of 7074%concentration are combined, the mixture heated to to F. (54-60 C.) andthe heated mixture transferred to a suitable mixing vessel.

(2) A premixed combination of sodium nitrate and guar gum is added andmixed for 3 /2 minutes until thickening is observed.

(3) The auxiliary fuels and carbonaceous non-explosive fuels are addedand the blend mixed until the fuels are uniformly incorporated.

-150%, said sensitizer component, other than said nitrogen-base salttherein, comprising less than about 50% by weight of high-explosivesensitizer.

2. An explosive of claim 1 wherein said nitrogen-base salt is the saltof an amine and nitric acid.

3. An explosive of claim 2 wherein said nitrogen-base salt is at leastone salt of nitric acid and an amine consisting of carbon, hydrogen andbasic nitrogen.

4. An explosive of claim 3 wherein said sensitizer consists essentiallyof at least one nitrogen-base salt of an aliphatic amine and nitricacid.

5. An explosive of claim 4 wherein said sensitizer consits essentiallyof a mixture of at least two of said nitrogen-base salts.

6. An explosive of claim 3 wherein said nitrogen-base salt is asaturated aliphatic amine nitrate of up to three carbon atoms.

7. An explosive of claim 6 wherein said nitrogen-base salt ismonomethylamine nitrate.

8. An explosive of claim 6 wherein said nitrogen-base salt isethylenediamine dinitrate.

9. An explosive of claim '6 wherein said nitrogen-base salt istrimethylamine nitrate.

10. An explosive of claim 3 wherein said nitrogen-base salt is anilinenitrate.

11. A gelled water-bearing explosive of claim 3 comprising, based on thetotal weight thereof, at least about 20% of said inorganic oxidizingsalt component, about from 10 to 50% of said nitric acid-amine saltcomponent, and about from 10 to 30% by weight of water.

12. An explosive of claim 11 wherein said inorganic oxidizing saltcomponent consists essentially of inorganic oxidizing salt at least 50%by weight of which is ammonium nitrate.

13. An explosive of claim 12 wherein said nitric acidamine saltcomponent is monomethylamine nitrate.

14. An explosive of claim 12 wherein said nitric acidamine saltcomponent is ethylenediamine dinitrate.

15. In the process for making water-bearing explosives which comprisesblending an inorganic oxidizing salt component, a fuel component andwater, the improvement which comprises blending in said explosive as asensitizer the reaction mixture obtained by reacting at least oneinorganic oxidizing acid with at least one base selected from the groupconsisting of (a) acyclic nitrogen bases having no more than twohydrogen atoms bonded to basic nitrogen and up to 3 carbons per basicnitrogen and (b) phenyl amines in water to yield 2. nitrogen-base salt,said nitrogen-base salt having an oxygen balance more positive thanISO%.

16. A process of claim 15 wherein said nitrogen-base salt is formed insaid aqueous medium then blended with the remainder of the constituentsof said explosive.

17. A process of claim 15 wherein said nitrogen-base salt is formed inwater in the presence of at least one other constituent of saidexplosive.

References Cited UNITED STATES PATENTS 2,947,618 8/ 1960 Stengel et al14992 3,013,382 12/1961 Doss 14992 X 3,031,839 5/1962 Larson 14992 X3,058,301 10/1962 Larsen et a1 149-92 X 3,088,272 5/1963 Stengel et al149-92 X 3,115,005 12/1963 Clark 149-92 X 3,125,852 3/1964 Blackwell eta1 149-92. X 3,212,254 10/1965 FOX 14992 X BENJAMIN R. PADGETT, PrimaryExaminer.

S. I. LECHERT, Assistant Examiner.

US. Cl. X.R.

